Process for the manufacture of branched polypropylene

Abstract

A process for manufacturing a branched polypropylene, said branched polypropylene having a branching index g′ of less than 1.00, the process comprising the step of polymerizing propylene and optionally one or more other comonomers under non-supercritical conditions in a reaction vessel, wherein: c. the pressure during the polymerization of propylene and optionally one or more other comonomers in said reaction vessel is at least 45.4 bar; d. the temperature during the polymerization of propylene and optionally one or more other comonomers in said reaction vessel is below 90° C.; and c. the polymerization of propylene and optionally one or more other comonomers is conducted in said reaction vessel in the presence of a catalyst system having a surface area of not more than 350 m 2 /g, measured according to ISO 9277, and said catalyst system comprises a metallocene catalyst having zirconium as the transition metal.

1. A process for manufacturing a branched polypropylene, said branched polypropylene having a branching index g′ of less than 1.00, the process comprising the step of polymerizing propylene and optionally one or more other comonomers under non-supercritical conditions in a reaction vessel, wherein:
 a. the pressure during the polymerization of propylene and optionally one or more other comonomers in said reaction vessel is at least 45.4 bar; 
 b. the temperature during the polymerization of propylene and optionally one or more other comonomers in said reaction vessel is below 90° C.; and 
 c. the polymerization of propylene and optionally one or more other comonomers is conducted in said reaction vessel in the presence of a catalyst system having a surface area of not more than 350 m 2 /g, measured according to ISO 9277, and said catalyst system comprises a metallocene catalyst having zirconium as the transition metal. 
 
     
     
       2. The process of  claim 1 , wherein said catalyst system has a pore volume of below 4.00 cm 3 /g, measured according to DIN 66135 (N 2 ). 
     
     
       3. The process of  claim 1 , wherein said catalyst system has a catalyst activity of at least 10 kg PP/g cat×h. 
     
     
       4. The process of  claim 1 , wherein the metallocene catalyst comprises two cyclopentadienyl rings of the same chemical formula. 
     
     
       5. The process of  claim 1 , wherein the metallocene catalyst comprises two cyclopentadienyl rings of a different chemical formula. 
     
     
       6. The process of  claim 1 , wherein the metallocene catalyst is not silica supported. 
     
     
       7. The process of  claim 1 , wherein the metallocene catalyst has the formula (I):
   (Cp) 2 R z ZrX 2   (I)
 
 Wherein: 
 z is 0 or 1; 
 X is independently a monovalent anionic ligand; 
 R is a bridging group linking the two Cp-ligands; and 
 the two Cp-ligands are selected, independently from each other, from the group consisting of unsubstituted cyclopentadienyl ring, unsubstituted indenyl ring, unsubstituted tetrahydroindenyl ring, unsubstituted fluorenyl ring, substituted cyclopentadienyl ring, substituted indenyl ring, substituted tetrahydroindenyl ring, and substituted fluorenyl ring. 
 
     
     
       8. The process of  claim 7 , wherein X is chlorine. 
     
     
       9. The process of  claim 7 , wherein:
 z is 1; and 
 R is —Si(CH 3 ) 2 —. 
 
     
     
       10. The process of  claim 7 , wherein the two Cp-ligands are selected, independently from each other, from the group consisting of unsubstituted indenyl ring and substituted indenyl ring. 
     
     
       11. The process of  claim 7 , wherein the substituents bonded to the ring are independently selected from the group consisting of C 1  to C 6  alkyl moiety, substituted aromatic ring moiety, unsubstituted aromatic ring moiety, substituted heteroaromatic ring moiety and unsubstituted heteroaromatic ring moiety. 
     
     
       12. The process of  claim 7 , wherein the two Cp-ligands are identical. 
     
     
       13. The process of  claim 7 , wherein the two Cp-ligands differ in their chemical structure. 
     
     
       14. The process of  claim 1 , wherein the metallocene catalyst is dimethylsilyl(2-methyl-4-phenyl-indenyl) 2 zirconium dichloride. 
     
     
       15. The process of  claim 7 , wherein the metallocene catalyst is dimethylsilyl(2-methyl-4-phenyl-indenyl) 2 zirconium dichloride. 
     
     
       16. The process of  claim 1 , wherein the metallocene catalyst is dimethylsilyl[(2-methyl-(4′-tert.butyl)-4-phenyl-indenyl)(2-isopropyl-(4′-tert.butyl)-4-phenyl-indenyl)]zirconium dichloride. 
     
     
       17. The process of  claim 7 , wherein the metallocene catalyst is dimethylsilyl[(2-methyl-(4′-tert.butyl)-4-phenyl-indenyl)(2-isopropyl-(4′-tert.butyl)-4-phenyl-indenyl)]zirconium dichloride. 
     
     
       18. The process of  claim 1 , wherein the comonomer is ethylene. 
     
     
       19. The process of  claim 1 , wherein the process is a bulk polymerization. 
     
     
       20. The process of  claim 1 , wherein the process is a combination of bulk polymerisation and gas phase polymerization. 
     
     
       21. The process of  claim 1 , wherein the obtained branched polypropylene has a pore volume below 5.00 cm 3 /g measured according to DIN 66135 (N 2 ). 
     
     
       22. The process of  claim 1 , wherein the obtained branched polypropylene has a melt drawability of more than 150 mm/s. 
     
     
       23. The process of  claim 1 , wherein the obtained branched polypropylene has a strain hardening index of at least 0.15 measured at a deformation rate, dε/dt, of 1.00 s −1  at a temperature of 180° C., wherein the strain hardening index is defined as a slope of a logarithm to the basis 10 of the tensile stress growth function as a function of a logarithm to the basis 10 of the Hencky strain in the range of Hencky strains between 1 and 3. 
     
     
       24. A process for manufacturing a branched polypropylene, said branched polypropylene having a branching index g′ of less than 1.00, the process comprising the step of polymerizing propylene and optionally one or more other comonomers under non-supercritical conditions in a reaction vessel, wherein
 a. the pressure during the polymerization of propylene and optionally one or more other comonomers in said reaction vessel is at least 45.4 bar; 
 b. the temperature during the polymerization of propylene and optionally one or more other comonomers in said reaction vessel is below 90° C.; and 
 c. the polymerization of propylene and optionally one or more other comonomers is conducted in said reaction vessel in the presence of a catalyst system having pore volume of below 3.50 cm 3 /g, measured according to DIN 66135 (N 2 ), and said catalyst system comprises a metallocene catalyst having zirconium as the transition metal. 
 
     
     
       25. The process of  claim 24 , wherein said catalyst system has a surface area of not more than 350 m 2 /g measured according to ISO 9277 (N 2 ).